Taming Nickel-Catalyzed Suzuki-Miyaura Coupling: A Mechanistic Focus on Boron-to-Nickel Transmetalation

Asymmetric 2,3-Addition of Sulfinylamines with Arylboronic Acids Enabled by Nickel Catalysis

Sulfinamides have been widely used in organic synthesis, with research on their preparation spanning more than a century. Despite advancements in catalytic methodologies, creating sulfur stereocenters within these molecules remains a significant challenge. In this study, we present an effective and versatile method for synthesizing a diverse range of S-chirogenic sulfinamides through catalytic asymmetric aryl addition to sulfinylamines. By utilizing a nickel complex as a catalyst, this process exhibits impressive enantioselectivity and can incorporate various arylboronic acids at the sulfur position. The resulting synthetic sulfinamides are stable and highly adaptable, allowing for their conversion to a variety of sulfur-containing compounds. Our study also incorporates detailed experimental and computational studies to elucidate the reaction mechanism and factors influencing enantioselectivity.

Nickel-Based Catalysts for the Selective Monoarylation of Dichloropyridines: Ligand Effects and Mechanistic Insights

This report describes a detailed study of Ni phosphine catalysts for the Suzuki-Miyaura coupling of dichloropyridines with halogen-containing (hetero)aryl boronic acids. With most phosphine ligands these transformations afford mixtures of mono- and diarylated cross-coupling products as well as competing oligomerization of the boronic acid. However, a ligand screen revealed that PPh2Me and PPh3 afford high yield and selectivity for monoarylation over diarylation as well as minimal competing oligomerization of the boronic acid. Several key observations were made regarding the selectivity of these reactions, including: (1) phosphine ligands that afford high selectivity for monoarylation fall within a narrow range of Tolman cone angles (between 136° and 157°); (2) more electron-rich trialkylphosphines afford predominantly diarylated products, while less-electron rich di- and triarylphosphines favor monoarylation; (3) diarylation proceeds via intramolecular oxidative addition; and (4) the solvent (MeCN) plays a crucial role in achieving high monoarylation selectivity. Experimental and DFT studies suggest that all these data can be explained based on the reactivity of a key intermediate: a Ni0-π complex of the monoarylated product. With larger, more electron-rich trialkylphosphine ligands, this π complex undergoes intramolecular oxidative addition faster than ligand substitution by the MeCN solvent, leading to selective diarylation. In contrast, with relatively small di- and triarylphosphine ligands, associative ligand substitution by MeCN is competitive with oxidative addition, resulting in selective formation of monoarylated products. The generality of this method is demonstrated with a variety of dichloropyridines and chloro-substituted aryl boronic acids. Furthermore, the optimal ligand (PPh2Me) and solvent (MeCN) are leveraged to achieve the Ni-catalyzed monoarylation of a broader set of dichloroarene substrates.

(Phenoxyimine)nickel-Catalyzed C(sp2)-C(sp3) Suzuki-Miyaura Cross-Coupling: Evidence for a Recovering Radical Chain Mechanism

Phenoxyimine (FI)-nickel(II)(2-tolyl)(DMAP) compounds were synthesized and evaluated as precatalysts for the C(sp2)-C(sp3) Suzuki-Miyaura cross coupling of (hetero)arylboronic acids with alkyl bromides. With 5 mol % of the optimal (MeOMeFI)Ni(Aryl)(DMAP) precatalyst, the scope of the cross-coupling reaction was established and included a variety of (hetero)arylboronic acids and alkyl bromides (>50 examples, 33-97% yield). A β-hydride elimination-reductive elimination sequence from reaction with potassium isopropoxide base, yielding a potassium (FI)nickel(0)ate, was identified as a catalyst activation pathway that is responsible for halogen atom abstraction from the alkyl bromide. A combination of NMR and EPR spectroscopies identified (FI)nickel(II)-aryl complexes as the resting state during catalysis with no evidence for long-lived organic radical or odd-electron nickel intermediates. These data establish that the radical chain is short-lived and undergoes facile termination and also support a "recovering radical chain" process whereby the (FI)nickel(II)-aryl compound continually (re)initiates the radical chain. Kinetic studies established that the rate of C(sp2)-C(sp3) product formation was proportional to the concentration of the (FI)nickel(II)-aryl resting state that captures the alkyl radical for chain propagation. The proposed mechanism involves two key and concurrently operating catalytic cycles; the first involving a nickel(I/II/III) radical propagation cycle consisting of radical capture at (FI)nickel(II)-aryl, C(sp2)-C(sp3) reductive elimination, bromine atom abstraction from C(sp3)-Br, and transmetalation; and the second involving an off-cycle catalyst recovery process by slow (FI)nickel(II)-aryl → (FI)nickel(0)ate conversion for nickel(I) regeneration.

ProPhos: A Ligand for Promoting Nickel-Catalyzed Suzuki-Miyaura Coupling Inspired by Mechanistic Insights into Transmetalation

Nickel-catalyzed Suzuki-Miyaura coupling (Ni-SMC) offers the potential to reduce the cost of pharmaceutical process synthesis. However, its application has been restricted by challenges such as slow reaction rates, high catalyst loading, and a limited scope of heterocycles. Despite recent investigations, the mechanism of transmetalation in Ni-SMC, often viewed as the turnover-limiting step, remains insufficiently understood. We elucidate the "Ni-oxo" transmetalation pathway, applying PPh2Me as the ligand, and identify the formation of a nickel-oxo intermediate as the turnover-limiting step. Building on this insight, we develop a scaffolding ligand, ProPhos, featuring a pendant hydroxyl group connected to the phosphine via a linker. The design preorganizes both the nucleophile and the nickel catalyst, thereby facilitating transmetalation. This catalyst exhibits fast kinetics and robust activity across a wide range of heteroarenes, with a catalyst loading of 0.5-3 mol %. For arene substrates, the catalyst loading can be further reduced to 0.1 mol %.

Phenoxythiazoline (FTz)-Cobalt(II) Precatalysts Enable C(sp2 )-C(sp3 ) Bond-Formation for Key Intermediates in the Synthesis of Toll-like Receptor 7/8 Antagonists

Evaluation of the relative rates of the cobalt-catalyzed C(sp2 )-C(sp3 ) Suzuki-Miyaura cross-coupling between the neopentylglycol ester of 4-fluorophenylboronic acid and N-Boc-4-bromopiperidine established that smaller N-alkyl substituents on the phenoxyimine (FI) supporting ligand accelerated the overall rate of the reaction. This trend inspired the design of optimal cobalt catalysts with phenoxyoxazoline (FOx) and phenoxythiazoline (FTz) ligands. An air-stable cobalt(II) precatalyst, (FTz)CoBr(py)3 was synthesized and applied to the cross-coupling of an indole-5-boronic ester nucleophile with a piperidine-4-bromide electrophile that is relevant to the synthesis of reported toll-like receptor (TLR) 7/8 antagonist molecules including afimetoran. Addition of excess KOMe⋅B(Oi Pr)3 improved catalyst lifetime due to attenuation of alkoxide basicity that otherwise resulted in demetallation of the FI chelate. A first-order dependence on the cobalt precatalyst and a saturation regime in nucleophile were observed, supporting turnover-limiting transmetalation and the origin of the observed trends in N-imine substitution.

DFT Mechanistic Insights into the Ni(II)-Catalyzed Enantioselective Arylative Cyclization of Tethered Allene-Ketones

Density functional theory (DFT) has provided a detailed mechanistic picture for the redox neutral nickel(II)-catalyzed arylative cyclization reactions of a tethered allene-ketone with arylboronic acids. A mechanistic rationale for the high diastereo- and enantioselectivity achieved experimentally at high reaction temperature was uncovered through modeling the reaction with a chiral ligand and the predicted stereochemical outcome corroborates with experimental results. An unprecedented mechanism for the base-free organoboron transmetalation was revealed and the regioselectivity of migratory insertion of tethered allene-ketones as well as the stability of the possible allylnickel isomers (σ-allyl vs π-allyl) were clarified. The multifaceted nature of the reaction is revealed with certain elementary steps preferring cationic compared to the neutral state.

Mechanistic Investigations of Phenoxyimine-Cobalt(II)-Catalyzed C(sp2)-C(sp3) Suzuki-Miyaura Cross-Coupling

The mechanism of phenoxyimine (FI)-cobalt-catalyzed C(sp2)-C(sp3) Suzuki-Miyaura cross-coupling was studied using a combination of kinetic measurements and catalytic and stoichiometric experiments. A series of dimeric (FI)cobalt(II) bromide complexes, [(4-CF3PhFI)CoBr]2, [(4-OMePhFI)CoBr]2, and [(2,6-diiPrPhFI)CoBr]2, were isolated and characterized by 1H and 19F NMR spectroscopies, solution and solid-state magnetic susceptibility, electron paramagnetic resonance (EPR) spectroscopy, X-ray crystallography, and diffusion-ordered NMR spectroscopy (DOSY). One complex, [(4-CF3PhFI)CoBr]2, was explored as a single-component precatalyst for C(sp2)-C(sp3) Suzuki-Miyaura cross-coupling. Addition of potassium methoxide to [(4-CF3PhFI)CoBr]2 generated the corresponding (FI)cobalt(II) methoxide complex as determined by 1H and 19F NMR and EPR spectroscopies. These spectroscopic signatures were used to identify this compound as the resting state during catalytic C(sp2)-C(sp3) coupling. Variable time normalization analysis (VTNA) of in situ catalytic 19F NMR spectroscopic data was used to establish an experimental rate law that was first-order in a (FI)cobalt(II) precatalyst, zeroth-order in the alkyl halide, and first-order in an activated potassium methoxide-aryl boronate complex. These findings are consistent with turnover-limiting transmetalation that occurs prior to activation of the alkyl bromide electrophile. The involvement of boronate intermediates in transmetalation was corroborated by Hammett studies of electronically differentiated aryl boronic esters. Together, a cobalt(II)/cobalt(III) catalytic cycle was proposed that proceeds through a "boronate"-type mechanism.

Comparison of Monophosphine and Bisphosphine Precatalysts for Ni-Catalyzed Suzuki-Miyaura Cross-Coupling: Understanding the Role of the Ligation State in Catalysis

Practical advances in Ni-catalyzed Suzuki-Miyaura cross-coupling (SMC) have been limited by a lack of mechanistic understanding of phosphine ligand effects. While bisphosphines are commonly used in these methodologies, we have observed instances where monophosphines can provide comparable or higher levels of reactivity. Seeking to understand the role of ligation state in catalysis, we performed a head-to-head comparison study of C(sp2)-C(sp2) Ni SMCs catalyzed by mono and bisphosphine precatalysts using six distinct substrate pairings. Significant variation in optimal precatalyst was observed, with the monophosphine precatalyst tending to outperform the bisphosphines with electronically deactivated and sterically hindered substrates. Mechanistic experiments revealed a role for monoligated (P1Ni) species in accelerating the fundamental organometallic steps of the catalytic cycle, while highlighting the need for bisligated (P2Ni) species to avoid off-cycle reactivity and catalyst poisoning by heterocyclic motifs. These findings provide guidelines for ligand selection against challenging substrates and future ligand design tailored to the mechanistic demands of Ni-catalyzed SMCs.

Mechanistic Study of the Copper(II)-Mediated Site-Selective O-Arylation of Glycosides with Arylboronic Acids

Glycosides having multiple free OH groups have been shown to undergo site-selective O-arylations in the presence of arylboronic acids and copper(II) acetate. Herein, a mechanistic analysis of these Chan-Evans-Lam-type couplings is presented based on reaction kinetics, mass spectrometric analysis of reaction mixtures, and substituent effect studies. The results establish that the formation of a substrate-derived boronic ester accelerates the rate-determining transmetalation step. Intramolecular transfer of the aryl group from the boronic ester is ruled out in favor of a pathway in which the key pre-transmetalation assembly is generated from a boronic ester, a copper complex, and a second equivalent of arylboronic acid.

DFT Study of Mechanism and Stereochemistry of Nickel-Catalyzed trans-Arylative Desymmetrizing Cyclization of Alkyne-Tethered Malononitriles

Present here is a density functional theory (DFT) study of the mechanism and origin of enantioselectivity of Ni-catalyzed desymmetric cyclization of alkyne-tethered malononitriles and aryl boronic acids. The reaction starts from transmetalation and arylnickel addition, followed by trans to cis isomerization to give cis-alkenyl nickel species. The stereodetermining step is the CN insertion, which prefers a transition state with the bystander CN group staying away from the ligand to reduce steric repulsion, and gives the final (R)-product.

Enabling Suzuki-Miyaura coupling of Lewis-basic arylboronic esters with a nonprecious metal catalyst

The high cost and negative environmental impact of precious metal catalysts has led to increased demand for nonprecious alternatives for widely practiced reactions such as the Suzuki-Miyaura coupling (SMC). Ni-catalyzed versions of this reaction have failed to achieve high reactivity with Lewis-basic arylboron nucleophiles, especially pinacolboron esters. We describe the development of (PPh2Me)2NiCl2 as an inexpensive and air-stable precatalyst that addresses this challenge. Under activation by n-BuMgCl, this complex can catalyze the coupling of synthetically important heteroaryl pinacolborons with heteroaryl halides. Mildly basic conditions (aqueous K3PO4) allow the reaction to tolerate sensitive functional groups that were incompatible with other Ni-SMC methods. Experimental and computational studies suggest that catalyst inhibition by substitution of PPh2Me from Ni(ii) intermediates by Lewis basic reactants and products is disfavored relative to more commonly employed ligands in the Ni-SMC, which allows it to operate efficiently in the presence of Lewis bases such as unhindered pyridines.

Copper-Catalyzed Homocoupling of Boronic Acids: A Focus on B-to-Cu and Cu-to-Cu Transmetalations

Controlling and understanding the Cu-catalyzed homocoupling reaction is crucial to prompt the development of efficient Cu-catalyzed cross-coupling reactions. The presence of a coordinating base (hydroxide and methoxide) enables the B-to-Cu(II) transmetalation from aryl boronic acid to CuIICl2 in methanol, through the formation of mixed Cu-(μ-OH)-B intermediates. A second B-to-Cu transmetalation to form bis-aryl Cu(II) complexes is disfavored. Instead, organocopper(II) dimers undergo a coupled transmetalation-electron transfer (TET) allowing the formation of bis-organocopper(III) complexes readily promoting reductive elimination. Based on this mechanism some guidelines are suggested to control the undesired formation of homocoupling product in Cu-catalyzed cross-coupling reactions.

Structure-Reactivity Relationships of Buchwald-Type Phosphines in Nickel-Catalyzed Cross-Couplings

The dialkyl-ortho-biaryl class of phosphines, commonly known as Buchwald-type ligands, are among the most important phosphines in Pd-catalyzed cross-coupling. These ligands have also been successfully applied to several synthetically valuable Ni-catalyzed cross-coupling methodologies and, as demonstrated in this work, are top performing ligands in Ni-catalyzed Suzuki Miyaura Coupling (SMC) and C-N coupling reactions, even outperforming commonly employed bisphosphines like dppf in many circumstances. However, little is known about their structure-reactivity relationships (SRRs) with Ni, and limited examples of well-defined, catalytically relevant Ni complexes with Buchwald-type ligands exist. In this work, we report the analysis of Buchwald-type phosphine SRRs in four representative Ni-catalyzed cross-coupling reactions. Our study was guided by data-driven classification analysis, which together with mechanistic organometallic studies of structurally characterized Ni(0), Ni(I), and Ni(II) complexes allowed us to rationalize reactivity patterns in catalysis. Overall, we expect that this study will serve as a platform for further exploration of this ligand class in organonickel chemistry as well as in the development of new Ni-catalyzed cross-coupling methodologies.

Stereoconvergent and -divergent Synthesis of Tetrasubstituted Alkenes by Nickel-Catalyzed Cross-Couplings

We report the development of a method to diastereoselectively access tetrasubstituted alkenes via nickel-catalyzed Suzuki-Miyaura cross-couplings of enol tosylates and boronic acid esters. Either diastereomeric product was selectively accessed from a mixture of enol tosylate starting material diastereomers in a convergent reaction by judicious choice of the ligand and reaction conditions. A similar protocol also enabled a divergent synthesis of each product isomer from diastereomerically pure enol tosylates. Notably, high-throughput optimization of the monophosphine ligands was guided by chemical space analysis of the kraken library to ensure a diverse selection of ligands was examined. Stereoelectronic analysis of the results provided insight into the requirements for reactive and selective ligands in this transformation. The synthetic utility of the optimized catalytic system was then probed in the stereoselective synthesis of various tetrasubstituted alkenes, with yields up to 94% and diastereomeric ratios up to 99:1 Z/E and 93:7 E/Z observed. Moreover, a detailed computational analysis and experimental mechanistic studies provided key insights into the nature of the underlying isomerization process impacting selectivity in the cross-coupling.

Univariate classification of phosphine ligation state and reactivity in cross-coupling catalysis

[Figure: see text].

Ni-catalyzed hydroalkylation of olefins with N-sulfonyl amines

Hydroalkylation, the direct addition of a C(sp³)–H bond across an olefin, is a desirable strategy to produce valuable, complex structural motifs in functional materials, pharmaceuticals, and natural products. Herein, we report a reliable method for accessing α-branched amines via nickel-catalyzed hydroalkylation reactions. Specifically, by using bis(cyclooctadiene)nickel (Ni(cod)₂) together with a phosphine ligand, we achieved a formal C(sp³)–H bond insertion reaction between olefins and N-sulfonyl amines without the need for an external hydride source. The amine not only provides the alkyl motif but also delivers hydride to the olefin by means of a nickel-engaged β–hydride elimination/reductive elimination process. This method provides a platform for constructing chiral α-branched amines by using a P-chiral ligand, demonstrating its potential utility in organic synthesis. Notably, a sulfonamidyl boronate complex formed in situ under basic conditions promotes ring-opening of the azanickellacycle reaction intermediate, leading to a significant improvement of the catalytic efficiency.

Catalytic addition of a carbon chain and a hydrogen across a double bond has often required an added hydride source. Here the authors show a method to add alkanes with an amino functionality to olefins, wherein a nickel catalyst uses the amine itself as the hydride source, obviating an external hydride reagent.

Nickel-Catalyzed, Stereospecific C-C and C-B Cross-Couplings via C-N and C-O Bond Activation

Highly enantioenriched benzylic and allylic amines and alcohols are readily available via asymmetric synthesis and in complex natural products. The development of mild, nickel-catalyzed cross-couplings of their derivatives has advanced the tools available for the preparation of a range of highly enantioenriched products, including those with quaternary stereocenters. This perspective focuses on cross-couplings with convenient and functional group-tolerant organoboron reagents and highlights the discoveries of activating groups and conditions that have led to high-yielding and highly stereospecific reactions. Emphasis is placed on mechanistic understanding, particularly with regards to controlling inversion vs. retention pathways. Limitations and opportunities for future developments are also highlighted.

Solar-driven tandem photoredox nickel-catalysed cross-coupling using modified carbon nitride

Nickel-catalysed aryl amination and etherification are driven with sunlight using a surface-modified carbon nitride to extend the absorption of the photocatalyst into a wide range of the visible region. In contrast to traditional homogeneous photochemical methodologies, the lower cost and higher recyclability of the metal-free photocatalyst, along with the use of readily available sunlight, provides an efficient and sustainable approach to promote nickel-catalysed cross-couplings.

Ancillary ligand electro-activity effects towards phenyl acetylene homocoupling reaction by a nickel(ii) complex of a non-innocent O-amino phenol ligand: a mechanistic insight

A new Ni(ii) complex, was synthesized from the reaction of a non-innocent o-aminophenol ligand, and Ni(OAc)₂. The crystal structure of Ni^IIL₂^NIS (in which, IS stands for iminosemiquinone radical ligand with cyanide (shown by N in NIS) substituent on phenolate rings) exhibits the square planar environment of Ni(ii). The complex has been crystalized in the monoclinic system and Ni(ii) was surrounded by two oxygen and two nitrogen atoms of two ligands. Variable-temperature magnetic susceptibility measurement for crystalline samples of complex shows the effective magnetic moment per molecule (μ_eff) of near zero and the diamagnetic nature of the complex (S = 0) which emphasize that strong antiferromagnetic coupling prevailed between the two unpaired electrons of L^NIS ligands and Ni(ii) high spin electrons. The complex is EPR silent which confirms the diamagnetic character of the Ni(ii) complex. Electrochemical measurement (CV) indicates the redox-active character of ligand and metal. Ni^IIL₂^NIS complex proved to be effective for free metal- or base counterpart homocoupling of phenyl acetylene at room temperature. To the best of our knowledge, this is the first example of using Ni(ii) complex without using any reducing agent due to the promotion ancillary effect of non-innocent o-aminophenol ligand which acts as an “electron reservoir” and can reversibly accept and donate electrons in the catalytic cycle. The theoretical calculation confirms the magnetostructure, electronic spectrum and confirmed the suggested mechanism of phenyl acetylene homocoupling with emphasis on the role of non-innocent ligand electro-activity and the effect of ligand substituent on the efficiency and stability of the complex.

A new Ni(ii) complex, was synthesized from the reaction of a non-innocent o-aminophenol ligand, and Ni(OAc)₂.

Terpyridine-based Pd(ii)/Ni(ii) organometallic framework nano-sheets supported on graphene oxide-investigating the fabrication, tuning of catalytic properties and synergetic effects

Tailoring the structures of catalysts and the arrangement of organic bimetallic catalysts are essential in both fundamental research and applications. However, they still impose enormous challenges such as size and active species distribution, ordered uniformity, and controllable composition, which are critical in determining their specific activities and efficiency. Herein, a novel terpyridine-based hetero-bimetallic Ni/Pd nanosheet supported on graphene oxide (denoted as GO@Tpy-Ni/Pd) was fabricated, which exhibited higher catalytic activity, substrate applicability and recyclability for the Suzuki coupling reaction under mild conditions. The catalytic mechanism was heterogeneous catalysis at the interface and the synergetic effect between Pd and Ni resulted in a little Ni(0)/Pd(0) cluster including Pd(ii)/Ni(ii) as a whole being formed through electron transfer on the catalytic surface. This phenomenon could be interpreted as the nanoscale clusters of Ni/Pd being the real active centre stabilized by the ligand and GO and the synergetic effect. The absorption and desorption of different substrates and products on Ni/Pd clusters, as calculated by DFT, was proved to be another key factor.

The synergistic effect between Ni and Pd atom was the crucial factor for enhancing catalytic activity.

Enantioselective Assembly of Cycloenones with a Nitrile-Containing All-Carbon Quaternary Center from Malononitriles Enabled by Ni Catalysis

Chiral nitriles are valuable molecules in modern organic synthesis and drug discovery. Selectively differentiating the two nitrile groups of widely available malononitrile derivatives is a straightforward yet underdeveloped route to construct enantioenriched nitriles. Here we report an enantioselective nickel-catalyzed desymmetrization of malononitriles for the generation of nitrile-containing all-carbon quaternary stereocenters. This protocol involves a nickel-catalyzed addition of aryl boronic acids to alkynes, followed by a selective nitrile insertion, providing unprecedented access to enantioenriched 5-7-membered α-cyano-cycloenones with a fully substituted olefin from a broad range of substrates. The synthetic utility of these nitrile products is demonstrated by gram-scale synthesis and conversion to several useful functional groups.

Copper nanoparticles supported on highly nitrogen-rich covalent organic polymers as heterogeneous catalysts for the ipso-hydroxylation of phenyl boronic acid to phenol

Here, we report the synthesis of highly nitrogen-rich covalent organic polymers as a solid heterogeneous catalyst for the oxidation of phenylboronic acid under atmospheric conditions in an aqueous medium to achieve very good yields up to 99%.

Mechanism and Scope of Nickel-Catalyzed Decarbonylative Borylation of Carboxylic Acid Fluorides

This Article describes the development of a base-free, nickel-catalyzed decarbonylative coupling of carboxylic acid fluorides with diboron reagents to selectively afford aryl boronate ester products. Detailed studies were conducted to assess the relative rates of direct transmetalation between aryl boronate esters and diboron reagents and a bisphosphine nickel(aryl)(fluoride) intermediate. These investigations revealed that diboron reagents undergo transmetalation with this Ni(aryl)(fluoride) intermediate at rates significantly faster than their aryl boronate ester congeners. Furthermore, the reactivity of both boron reagents toward transmetalation is enhanced with increasing electrophilicity of the boron center. These mechanistic insights were leveraged to develop a catalytic decarbonylative borylation of acid fluorides that proved applicable to a variety of (hetero)aryl carboxylic acid fluorides as well as diverse diboron reagents. The acid fluorides can be generated in situ directly from carboxylic acids. Furthermore, the mechanistic studies directed the identification of various air-stable Ni pre-catalysts for this transformation.

A synthetic chemist's guide to electroanalytical tools for studying reaction mechanisms

Monitoring reactive intermediates can provide vital information in the study of synthetic reaction mechanisms, enabling the design of new catalysts and methods. Many synthetic transformations are centred on the alteration of oxidation states, but these redox processes frequently pass through intermediates with short life-times, making their study challenging. A variety of electroanalytical tools can be utilised to investigate these redox-active intermediates: from voltammetry to in situ spectroelectrochemistry and scanning electrochemical microscopy. This perspective provides an overview of these tools, with examples of both electrochemically-initiated processes and monitoring redox-active intermediates formed chemically in solution. The article is designed to introduce synthetic organic and organometallic chemists to electroanalytical techniques and their use in probing key mechanistic questions.